I assume this is going to be a webserver? Why do you need NAT? That's only useful for network traffic that starts on one network (internal?) and is supposed to end up on a different network (internet?). If the traffic starts on your server, or if the traffic is going to your server, you don't need NAT. NAT is for routers, really.

I'm still confused as to why you need to use NAT. Firewall, yes, of course, but NAT (Network Address Translation), is for transparently redirecting network traffic. What traffic is it that you are redirecting, and where are you sending it?
Are you trying to only allow certain ip's to connect with ssh? You don't need NAT for that, just iptables/ipchains.